Prosthetic cardiac valves have been used for many years to treat cardiac valvular disorders. The native heart valves (such as the aortic, pulmonary and mitral valves) serve critical functions in assuring the forward flow of an adequate supply of blood through the cardiovascular system. These heart valves can be rendered less effective by congenital, inflammatory or infectious conditions. Such damage to the valves can result in serious cardiovascular compromise or death. For many years the definitive treatment for such disorders was the surgical repair or replacement of the valve during open heart surgery, but such surgeries are prone to many complications. More recently a transvascular technique has been developed for introducing and implanting a prosthetic heart valve using a flexible catheter in a manner that is less invasive than open heart surgery.
In this technique, a prosthetic valve is mounted in a crimped state on the end portion of a flexible catheter and advanced through a blood vessel of the patient until the valve reaches the implantation site. The valve at the catheter tip is then expanded to its functional size at the site of the defective native valve such as by inflating a balloon on which the valve is mounted.
Another known technique for implanting a prosthetic aortic valve is a transapical approach where a small incision is made in the chest wall of a patient and the catheter is advanced through the apex (i.e., bottom tip) of the heart. Transapical techniques are disclosed in U.S. Patent Application Publication No. 2007/0112422, which is hereby incorporated by reference. Like the transvascular approach, the transapical approach includes a balloon catheter having a steering mechanism for delivering a balloon-expandable prosthetic heart valve through an introducer to the aortic annulus. The balloon catheter includes a deflecting segment just proximal to the distal balloon to facilitate positioning of the prosthetic heart valve in the proper orientation within the aortic annulus.
The above techniques and others have provided numerous options for high-risk patients with aortic valve stenosis to avoid the consequences of open heart surgery and cardiopulmonary bypass. While procedures for the aortic valve are well-developed, such procedures are not necessarily applicable to the mitral valve.
Mitral valve repair has increased in popularity due to its high success rates, and clinical improvements noted after repair. However, a significant percentage (i.e., about 33%) of patients still receive open-heart surgical mitral valve replacements due to calcium, stenosis, or anatomical limitations. There are a number of technologies aimed at making mitral repair a less invasive procedure. These technologies range from iterations of the Alfieri stitch procedure to coronary sinus-based modifications of mitral anatomy to subvalvular placations or ventricular remodeling devices, which would incidently correct mitral regurgitation.
However, for mitral valve replacement, few less-invasive options are available. There are approximately 60,000 mitral valve replacements (MVR) each year and it is estimated that another 60,000 patients should receive MVR, but are denied the surgical procedure due to risks associated with the patient's age or other factors. One potential option for a less invasive mitral valve replacement is disclosed in U.S. Patent Application 2007/0016286 to Herrmann. However, the stent disclosed in that application has a claw structure for attaching the prosthetic valve to the heart. Such a claw structure could have stability issues and limit consistent placement of a transcatheter mitral replacement valve.
Accordingly, further options are needed for less-invasive mitral valve replacement.